618 



SCIENCE 



[N. S. Vol. LII. No. 1357 



tirely tlie outlook upon the problems that 

 bacteriologists set themselves to solve. 



Behring and Kitasato chose the task of in- 

 ducing in animals immunity, to diphtheria 

 on the one hand and to tetanus on the other. 

 This was a logical undertaking and one 

 clearly in the spirit of the times. Both men 

 had a strong interest in the quest. The one 

 (Behring) was deeply engaged in the investi- 

 gation of the chemical disinfectants and con- 

 ceived ideas of modifying bacterial growth 

 through these agents, as Pasteur had succeeded 

 in accomplishing with physical means. The 

 other (Kitasato) had succeeded where his pre- 

 decessor and the discoverer of the tetanus ba- 

 cillus, ISTicolaier, had failed in obtaining pure 

 cultures of that microbe. Moreover, the re- 

 stricted local development of the two bacilli 

 and their generally poisonous or toxic efFects 

 aroused in them an eager interest intensified 

 by the epochal discovery just made by Eous 

 and Tersin that the toxin of the diphtheria 

 bacillus was readily separable from the bacilli 

 producing it and could be obtained by pre- 

 cipitation in,' it is true, an impure state but 

 one in which its poisonous action was pre- 

 served. Indeed, so appalling did its poison- 

 ous eJIect prove to be that these investigators 

 could not imagine any other non-living sub- 

 stance than an enzyme which could exhibit 

 such active properties. 



The isolation of the diphtheria toxin, 

 quickly to be followed by the similar isolation 

 of the tetanus toxin, was an event of capital 

 importance and reacted at once vigorously on 

 the chemical aspects of bactei'iology just 

 struggling into the light. The immediate 

 effect of the study of the new poisons, called 

 toxalbumins, was to discredit a whole series 

 of pure, crystalline basic substances obtained 

 not long before from a wide variety of bac- 

 teria, to which the name of ptomaines had 

 been given. Many of the ptomaines were pos- 

 sessed of poisonous properties; but what was 

 disconcerting was that very diverse bacteria 

 might yield identical chemical compounds 

 which, therefore, lacked the property of spe- 

 cificity, an essential quality of bacterial 

 activity. The toxalbumins, on the other hand. 



which even to this day have not been secured 

 in a chemically pure state, exhibit in perfect 

 degree the property of specificity and display 

 all the power for evil and all the potential 

 possibilities for good which their original and 

 respective bacilli possess; and although no 

 method of chemical identification of their 

 special nature is available, yet their patho- 

 logical effects and immunological activities 

 serve readily and accurately to distinguish 

 one from the other and to indicate their 

 origin. 



The rendering of animals immune to diph- 

 theria, on the one hand and to tetanus on the 

 other, proved a difficult but not impossible 

 task. The method adopted was to admix dis- 

 infectant chemicals, of which the one finally 

 selected was iodin trichlorid, with the bacilli 

 to be injected under the skin of animals, or 

 with the contents of the culture fiasks at the 

 end of the incubation period. Obviously, the 

 intent was to moderate the poisonous action of 

 the inoculated material, in the hope that a 

 mild and not fatal infection would be induced 

 from which recovery would follow leaving the 

 treated animal i mrm ine. 



The experiments were sometimes successful, 

 and as such seem merely to illustrate a varia- 

 tion of the Pasteuxian method of inducing 

 immunity which, as we saw, was not distinct 

 in principle from the Jennerian vaccination. 

 But the break with the past was none the less 

 imminent, for Behring's next act was not to 

 speculate on the theory of immimity but to 

 perform a decisive experiment. It is to be 

 kept in mind that in the poisons or toxal- 

 bumins of diphtheria and tetanus, we possess 

 the essentially active ingredients of the re- 

 spective bacilli and that the body attacked 

 does not succumb to the invading bacilli but 

 to the action of the toxins. Hence, Behring 

 turned to the blood of the immune animals and 

 tested it for neutralizing power against the 

 poisons, and discovered antitoxin; he injected 

 the blood of an immune into the body of a 

 normal animal prior to inoculation and dis- 

 covered passive immunization; and finally, he 

 injected the blood of an immune animal into 

 animals previously inoculated with the baciUi 



